At last week's Guadec meeting, Kristian Rietveld delivered the GTK+ "state of the union" report. GTK+ is the multi-platform toolkit behind a number of popular applications and, perhaps most well known, the Gnome Desktop environment for Linux. Read the full report here.

With Objective C it would not be easy to have bindings for static typed languages. Also the Smalltalk-style syntax doesn't map very well to most other languages.
I think GTK+ 3.0 should be implemented in Vala (at least partially). It's designed for the GObject type system and results in the same ABI as C libraries.